JP6187810B2 - Manufacturing method of ceramic sintered body - Google Patents
Manufacturing method of ceramic sintered body Download PDFInfo
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- JP6187810B2 JP6187810B2 JP2013180949A JP2013180949A JP6187810B2 JP 6187810 B2 JP6187810 B2 JP 6187810B2 JP 2013180949 A JP2013180949 A JP 2013180949A JP 2013180949 A JP2013180949 A JP 2013180949A JP 6187810 B2 JP6187810 B2 JP 6187810B2
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- 239000000919 ceramic Substances 0.000 title claims description 204
- 238000004519 manufacturing process Methods 0.000 title claims description 22
- 238000005238 degreasing Methods 0.000 claims description 139
- 238000000034 method Methods 0.000 claims description 84
- 239000000843 powder Substances 0.000 claims description 82
- 239000011230 binding agent Substances 0.000 claims description 77
- 230000008569 process Effects 0.000 claims description 55
- 239000000463 material Substances 0.000 claims description 31
- 238000005245 sintering Methods 0.000 claims description 29
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 27
- 235000012239 silicon dioxide Nutrition 0.000 claims description 17
- 229910002026 crystalline silica Inorganic materials 0.000 claims description 15
- 239000002245 particle Substances 0.000 claims description 8
- 238000005266 casting Methods 0.000 claims description 5
- 238000009826 distribution Methods 0.000 claims description 5
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- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000005350 fused silica glass Substances 0.000 description 4
- 239000012188 paraffin wax Substances 0.000 description 4
- 230000008439 repair process Effects 0.000 description 4
- 230000008961 swelling Effects 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- 230000008602 contraction Effects 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
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- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
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- 239000000377 silicon dioxide Substances 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910052845 zircon Inorganic materials 0.000 description 2
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910021532 Calcite Inorganic materials 0.000 description 1
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- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
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- 238000010079 rubber tapping Methods 0.000 description 1
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- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
- 230000008016 vaporization Effects 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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Description
本発明は、セラミック粉末とバインダを含んで形成されているセラミック成形体を用いるセラミック焼結体の製造方法に関する。 The present invention relates to a method for manufacturing a ceramic sintered body using a ceramic molded body formed by including ceramic powder and a binder.
セラミック成形体は、一般に、セラミック粉末とバインダを含み、射出成形法や鋳込み成形法によって形成されている。これらの成形法において、成形に必要な流動性や可塑性を得るためのバインダは、脱脂工程において加熱により溶融、分解、気化され、セラミック成形体から除去される。脱脂後のセラミック成形体（脱脂体）は、焼成工程においてセラミック粉末が焼結する温度まで加熱され、セラミック焼結体に形成される。このように形成されたセラミック焼結体は、硬くて脆いため機械加工が難しい。したがって、セラミック焼結体を製造する場合は、目標とする外形寸法に対する寸法バラツキができる限り小さいことが望まれる。 The ceramic molded body generally includes ceramic powder and a binder, and is formed by an injection molding method or a casting method. In these molding methods, the binder for obtaining fluidity and plasticity necessary for molding is melted, decomposed and vaporized by heating in the degreasing process, and removed from the ceramic molded body. The ceramic molded body (degreasing body) after degreasing is heated to a temperature at which the ceramic powder is sintered in the firing step, and formed into a ceramic sintered body. The ceramic sintered body formed in this way is hard and brittle, so that machining is difficult. Therefore, when manufacturing a ceramic sintered body, it is desired that the dimensional variation with respect to the target outer dimension is as small as possible.
セラミック焼結体の外形寸法のバラツキを低減することを目的とし、種々の製造方法が検討されている。例えば、特許文献１乃至３には、セラミック成形体を専用容器（サヤ）内に入れた敷粉の中に埋設し、加熱してバインダなどを除去（脱脂工程）し、さらに加熱してセラミック粉末を焼結する（焼成工程）方法が開示されている。この方法によれば、敷粉を用いてセラミック成形体の表面を被覆することにより、脱脂工程や焼成工程におけるセラミック成形体や脱脂体の変形が抑制できるとされる。 Various manufacturing methods have been studied for the purpose of reducing variations in the external dimensions of the ceramic sintered body. For example, in Patent Documents 1 to 3, a ceramic molded body is embedded in a bed powder placed in a special container (sheath), heated to remove a binder or the like (degreasing process), and further heated to ceramic powder. Is disclosed (sintering process). According to this method, it is said that the deformation of the ceramic molded body and the degreased body in the degreasing process and the firing process can be suppressed by covering the surface of the ceramic molded body with the bed powder.
また、例えば、特許文献４には、匣鉢（サヤ）内にセラミック成形体と同じ材質の敷粉を層状に敷き詰め、その上にセラミック成形体を載置した状態で焼成する方法が開示されている。この方法によれば、敷粉を用いてセラミック成形体とサヤの間の摩擦抵抗を軽減することにより、焼成工程における脱脂体の不均一な収縮変形が抑制できるとされる。 Further, for example, Patent Document 4 discloses a method in which a powder of the same material as the ceramic molded body is laid in layers in a sagger and fired in a state where the ceramic molded body is placed thereon. Yes. According to this method, non-uniform shrinkage deformation of the degreased body in the firing step can be suppressed by reducing the frictional resistance between the ceramic molded body and the sheath using the floor powder.
また、例えば、特許文献５、６には、タービンブレードなどの中空の翼形状を有する鋳物の製造に使用するセラミック中子の製造方法が開示されている。この方法は、焼成工程において敷粉ではなくセッターを使用し、その寝床の受け面をセラミック成形体に有する翼形状に対応する形状に形成するとされる。また、その寝床は、剛性のある材料で構成するとされ、具体的に、セラミック粉末（例えばアルミナ、シリカ、ジルコンおよび／またはジルコニア粉末）とその他の液体結合剤や添加剤を含んでなる混合物を用いて成形体を形成し、その成形体を焼結体に形成して寝床に使用する一例が記載されている。このような記載からして、その寝床の受け面は、一般のセラミック焼結体と同等の構造を有し、同程度に硬くかつ緻密に形成されていると推量される。 For example, Patent Documents 5 and 6 disclose a method for manufacturing a ceramic core used for manufacturing a casting having a hollow blade shape such as a turbine blade. In this method, a setter is used instead of the bed powder in the firing step, and the receiving surface of the bed is formed into a shape corresponding to the shape of the wing having the ceramic molded body. Further, the bed is made of a rigid material, and specifically, a mixture containing ceramic powder (for example, alumina, silica, zircon and / or zirconia powder) and other liquid binders and additives is used. An example of forming a molded body, forming the molded body into a sintered body, and using it for a bed is described. From such description, it is assumed that the receiving surface of the bed has a structure equivalent to that of a general ceramic sintered body and is formed to be as hard and dense as the same.
また、例えば、特許文献７には、焼成治具（サヤ）内に入れたセラミック粉体をタッピングして粉体ベッド（寝床）を形成し、さらにその寝床の上にセラミック成形体と同程度の収縮率を有する好ましくは同じ材質の成形板を設置する方法が開示されている。そして、焼成工程において、その成形板の上にセラミック成形体を載置し、セラミック粉末を焼結するとされる。この方法によれば、成形板がセラミック成形体とともに焼結して収縮することでセラミック成形体とサヤの間の摩擦抵抗が軽減され、焼成工程における変形やクラックを抑制できるとされる。 Further, for example, in Patent Document 7, a powder bed (bed) is formed by tapping ceramic powder placed in a firing jig (sheath), and further on the same level as the ceramic molded body. A method is disclosed in which a molded plate of preferably the same material having a shrinkage rate is installed. And in a baking process, it is supposed that a ceramic molded body is mounted on the shaping | molding board and a ceramic powder is sintered. According to this method, the molded plate is sintered and contracted together with the ceramic molded body, whereby the frictional resistance between the ceramic molded body and the sheath is reduced, and deformation and cracks in the firing process can be suppressed.
上述した特許文献１乃至３に開示される方法では、セラミック成形体の形状や敷粉への埋設状態によっては、焼成工程において、脱脂体が焼結して収縮するときに表面を被覆する敷粉がその収縮に追従できず、脱脂体の収縮を妨げてしまう問題があった。また、セラミック成形体がサヤに直接接触していると、脱脂や焼結の過程において、セラミック成形体や脱脂体がサヤの表面形状に倣うように変形してしまう問題があった。 In the methods disclosed in Patent Documents 1 to 3 described above, depending on the shape of the ceramic molded body and the state embedded in the floor powder, the floor powder that covers the surface when the degreased body sinters and contracts in the firing step. However, there was a problem that the contraction of the degreased body was hindered due to failure to follow the contraction. Further, when the ceramic molded body is in direct contact with the sheath, there is a problem that the ceramic molded body and the degreased body are deformed so as to follow the surface shape of the sheath in the process of degreasing and sintering.
また、上述した特許文献４に開示される方法では、セラミック成形体と同じ材質の敷粉がセラミック成形体に付着したまま焼結する問題があった。また、脱脂の過程で溶融したバインダが層状に形成された敷粉の内部に浸透する際に、バインダが浸透した敷粉層の表面が変形することがあり、セラミック成形体がその変形した敷粉層の形状に倣うように変形してしまう問題があった。 Moreover, in the method disclosed in Patent Document 4 described above, there is a problem that the powder of the same material as the ceramic molded body is sintered while attached to the ceramic molded body. In addition, when the binder melted in the degreasing process penetrates into the layered bed powder, the surface of the bed powder layer into which the binder has penetrated may be deformed, and the ceramic molded body may be deformed. There has been a problem of deformation to follow the shape of the layer.
また、上述した特許文献５、６に開示される方法では、セラミック焼結体でなる緻密で空隙率がかなり小さい硬い寝床の受け面にセラミック成形体を載置するため、脱脂の過程で溶融したバインダが寝床の内部にほとんど浸透せず、セラミック成形体と寝床の受け面との間に、つまりセラミック成形体の表面近傍に残留してしまう。このため、セラミック成形体の表面近傍に残留しているバインダが分解し気化する過程で、セラミック成形体に膨れや割れあるいは変形を生じる問題があった。 Further, in the methods disclosed in Patent Documents 5 and 6 described above, the ceramic molded body is placed on the receiving surface of a hard bed that is a dense ceramic sintered body and has a considerably low porosity, and thus melted during the degreasing process. The binder hardly penetrates into the bed and remains between the ceramic molded body and the receiving surface of the bed, that is, near the surface of the ceramic molded body. For this reason, there has been a problem that the ceramic molded body is swollen, cracked or deformed in the process in which the binder remaining in the vicinity of the surface of the ceramic molded body is decomposed and vaporized.
また、上述した特許文献７に開示される方法では、セラミック成形体と同程度の収縮率を有する好ましくは同じ材質の成形板にセラミック成形体を載置するため、成形板が焼結の過程で脱脂体とともに収縮して焼結し、セラミック焼結体の取り外しが困難になる、相互に固着するなどの問題があった。また、脱脂の過程で溶融したバインダがセラミック成形体と成形板の間に残留した場合には、脱脂体に膨れや割れを生じる問題があった。 Further, in the method disclosed in Patent Document 7 described above, since the ceramic molded body is placed on a molded board having the same degree of shrinkage as that of the ceramic molded body, preferably of the same material, the molded board is in the process of sintering. There were problems such as shrinking and sintering together with the degreased body, making it difficult to remove the ceramic sintered body, and sticking to each other. Further, when the binder melted in the degreasing process remains between the ceramic molded body and the molded plate, there has been a problem that the degreased body is swollen or cracked.
本発明の目的は、脱脂工程や焼成工程において、セラミック成形体や脱脂体に生じる膨れや割れあるいは変形といった問題を解決でき、目標とする外形寸法に対する寸法バラツキがより小さいセラミック焼結体の製造方法を提供することである。 An object of the present invention is a method for producing a ceramic sintered body that can solve problems such as blistering, cracking, or deformation occurring in a ceramic molded body or a degreased body in a degreasing process or a firing process, and that has a smaller dimensional variation with respect to a target external dimension. Is to provide.
本発明者は、脱脂工程や焼成工程におけるセラミック成形体や脱脂体の載置方法に着目し、セラミック成形体や脱脂体を載置する寝床とその受け面の適正化により、上述した課題が解決できることを見出し、本発明に到達した。 This inventor pays attention to the mounting method of the ceramic molded body and the degreased body in the degreasing process and the firing process, and the problem described above is solved by optimizing the bed and the receiving surface on which the ceramic molded body and the degreased body are placed. We have found out that we can do it and have reached the present invention.
すなわち、本発明は、セラミック粉末とバインダを含んで形成されているセラミック成形体を、脱脂工程および／または焼結工程において寝床に設けた受け面で支持する、ガスタービン翼の鋳造に用いる翼形部とダブテールを有するセラミック中子を形成するためのセラミック焼結体の製造方法であって、前記セラミック成形体の被載置部に対応する形状の転写部を有する模型を容器内に設置し、前記セラミック成形体の焼結処理条件において焼結されない粉末材料を前記転写部を被覆するように前記容器内に充填して振動を加えることにより、前記寝床の前記受け面を、前記セラミック成形体の前記被載置部に対応する形状であって、被測定箇所に対して垂直方向に測定した表面硬さが０．２〜４０ｋＰａの範囲内であるように形成する、ことを特徴とする。 That is, the present invention relates to an airfoil used for casting a gas turbine blade, in which a ceramic formed body including ceramic powder and a binder is supported by a receiving surface provided on a bed in a degreasing process and / or a sintering process. A ceramic sintered body manufacturing method for forming a ceramic core having a portion and a dovetail , wherein a model having a transfer portion having a shape corresponding to a placement portion of the ceramic molded body is installed in a container, by applying vibration by filling a powder material which is not sintered in the container so as to cover the transfer section in the sintering process conditions of the ceramic molded body, the receiving surface of said bed, said ceramic molded body wherein a shape corresponding to the mounting portion, the surface hardness measured in a direction perpendicular to the measured point is formed to be within the scope of 0.2～40KPa, And wherein the door.
本発明において、前記寝床を形成する粉末材料には、体積粒度分布におけるメジアン径ｄ５０が３〜４０μｍの粉末を用いることが好ましい。
また、前記寝床を形成する粉末材料には結晶性シリカ粉末を用いることが好ましい。
In the present invention, the powder material forming the bed, the median size d 50 in the volume particle size distribution is preferably used powder 3～40Myuemu.
Moreover, it is preferable to use crystalline silica powder as the powder material forming the bed.
また、前記脱脂工程は、バインダが分解し始めてから目標温度（２３０〜３５０℃）に到達するまでの低温脱脂工程より高い温度による高温脱脂工程とを有することが好ましい。
また、前記低温脱脂に用いる寝床（低温脱脂用寝床）の受け面における表面硬さを０．２〜１０ｋＰａとし、前記高温脱脂に用いる寝床（高温脱脂用寝床）の受け面における表面硬さを２〜４０ｋＰａとする、ことが好ましい。
また、前記低温脱脂は、前記セラミック成形体に含まれる前記バインダの残量が、前記低温脱脂工程前後のバインダ質量比で１０〜２０％になるように行う、ことが好ましい。
また、前記低温脱脂は、前記バインダが分解し始めた後は、昇温速度を５℃／ｈ以下に設定する、ことが好ましい。
また、前記低温脱脂工程と前記高温脱脂工程の間で前記寝床を交換し、前記高温脱脂工程に続いて前記焼結工程を行うことが好ましい。
また、前記低温脱脂工程に用いる寝床の受け面における表面硬さよりも前記高温脱脂に用いる寝床の受け面における表面硬さが硬いことが好ましい。
Moreover, it is preferable that the said degreasing process has a high temperature degreasing process by temperature higher than the low temperature degreasing process until it reaches target temperature (230-350 degreeC) after a binder begins to decompose | disassemble.
The surface hardness of the receiving surface of the bed used for the low temperature degreasing (low temperature degreasing bed) is 0.2 to 10 kPa, and the surface hardness of the receiving surface of the bed used for the high temperature degreasing (high temperature degreasing bed) is 2 It is preferable to be set to ˜40 kPa.
Moreover, it is preferable to perform the said low temperature degreasing so that the residual amount of the said binder contained in the said ceramic molded body may be 10-20% by the binder mass ratio before and behind the said low temperature degreasing process.
In the low temperature degreasing, it is preferable to set the heating rate to 5 ° C./h or less after the binder starts to decompose.
Moreover, it is preferable to replace the bed between the low temperature degreasing step and the high temperature degreasing step, and to perform the sintering step subsequent to the high temperature degreasing step.
Moreover, it is preferable that the surface hardness in the receiving surface of the bed used for the said high temperature degreasing is harder than the surface hardness in the receiving surface of the bed used in the said low temperature degreasing process.
本発明によれば、脱脂工程や焼成工程において、セラミック成形体や脱脂体に生じる膨れや割れあるいは変形といった欠陥の発生を抑制でき、目標とする外形寸法に対する寸法バラツキが小さいセラミック焼結体を形成することができる。 According to the present invention, it is possible to suppress the occurrence of defects such as blistering, cracking or deformation occurring in a ceramic molded body or a degreased body in a degreasing process or a firing process, and to form a ceramic sintered body with small dimensional variation with respect to a target external dimension. can do.
本発明における重要な特徴は、脱脂工程や焼成工程において、セラミック成形体や脱脂体を載置するための寝床とその受け面を適正化したことである。具体的には、以下を特徴とする。
（１）寝床をセラミック成形体の焼結処理条件において焼結されない粉末材料を用いて形成する。
（２）寝床の受け面をセラミック成形体の被載置部に対応する形状に形成する。
An important feature of the present invention is that the bed and the receiving surface for mounting the ceramic molded body and the degreased body are optimized in the degreasing process and the firing process. Specifically, it has the following features.
(1) The bed is formed using a powder material that is not sintered under the sintering treatment conditions of the ceramic molded body.
(2) The receiving surface of the bed is formed in a shape corresponding to the placement portion of the ceramic molded body.
以下、本発明に用いられる寝床について、詳細に説明する。
本発明に用いられる寝床は、セラミック粉末とバインダを含んで形成されているセラミック成形体を、脱脂工程および／または焼結工程において載置するためのものであり、粉末材料を用いて形成する。粉末材料を用いて形成した寝床は、毛細管現象が起こりやすく、脱脂過程でセラミック成形体から溶融したバインダの浸透を容易にすることができる。これにより、セラミック成形体の表面の極近傍にバインダが残留することを防止し、バインダの溶融、分解、気化に起因するセラミック成形体の膨れや割れあるいは変形を抑止することができる。なお、本発明の適用が好ましいセラミック成形体の一例を図４で示す。このセラミック成形体は、ガスタービン翼の鋳造に用いる翼形部８とダブテール９を有するセラミック中子に形成され、該セラミック中子はガスタービン翼の内部で中空構造となる冷却孔の形成に必要となる。このような薄肉で孔部や曲面部を有する複雑な形状を有するようなセラミック成形体への本発明の適用は特に好ましい。
Hereinafter, the bed used in the present invention will be described in detail.
The bed used in the present invention is for placing a ceramic molded body formed containing ceramic powder and a binder in a degreasing process and / or a sintering process, and is formed using a powder material. The bed formed using the powder material is likely to have a capillary phenomenon, and can easily penetrate the binder melted from the ceramic molded body in the degreasing process. Thereby, it is possible to prevent the binder from remaining in the very vicinity of the surface of the ceramic molded body, and to suppress swelling, cracking or deformation of the ceramic molded body due to melting, decomposition, or vaporization of the binder. An example of a ceramic molded body to which the present invention is preferably applied is shown in FIG. This ceramic molded body is formed in a ceramic core having an airfoil 8 and a dovetail 9 used for casting a gas turbine blade, and the ceramic core is necessary for forming a cooling hole having a hollow structure inside the gas turbine blade. It becomes. The application of the present invention to such a thin ceramic body having a complicated shape having a hole or a curved surface is particularly preferable.
また、本発明に係る寝床に用いる粉末材料は、前記（１）に示すように、対象とするセラミック成形体の焼結処理条件において焼結されない粉末材料を選定することが重要である。その理由は、上述した焼結処理条件において焼結しない粉末材料であれば、その粉末材料がたとえセラミック成形体や脱脂体の表面に付着していたとしても、最終的にセラミック焼結体の表面に異物となって固着することがないからである。 In addition, as shown in the above (1), it is important that the powder material used for the bed according to the present invention is a powder material that is not sintered under the sintering process conditions of the target ceramic molded body. The reason for this is that if the powder material does not sinter under the above-mentioned sintering conditions, the surface of the ceramic sintered body will eventually be obtained even if the powder material adheres to the surface of the ceramic molded body or degreased body. It is because it does not become a foreign material and adheres.
また、本発明においては、上述した寝床に対し、セラミック成形体や脱脂体に接触してこれを支持する受け面を設ける。その受け面は、前記（２）に示すように、対象とするセラミック成形体の被載置部に対応する形状に形成することが重要である。すなわち、受け面の形状を被載置部の形状を忠実に倣った形状あるいは大まかに倣った形状に形成するのである。被載置部に、例えば凹部や孔部あるいは突出高さの小さい凸部を有していたとしても、受け面としては必ずしも倣わなくてすむ場合もある。これにより、セラミック成形体と寝床の間に不要な隙間がなくなり、脱脂過程では、セラミック成形体や脱脂体の表面の極近傍へのバインダの残留が抑止でき、および、バインダの軟化により変形しやすくなったセラミック成形体がより的確に支持でき、脱脂体の有害な膨れや割れあるいは変形を抑止できる。また、焼成過程では、脱脂体を的確に支持できるため、セラミック粉末の焼結により収縮していく脱脂体の有害な変形を抑止できる。よって、目標とする外形寸法に対する寸法バラツキがより小さいセラミック焼結体を形成できる。 Moreover, in this invention, the receiving surface which contacts a ceramic molded body and a degreased body and supports this is provided with respect to the bed mentioned above. As shown in the above (2), it is important that the receiving surface is formed in a shape corresponding to the placement portion of the target ceramic molded body. That is, the shape of the receiving surface is formed into a shape that closely follows the shape of the placement portion or a shape that roughly follows it. Even if the mounting portion has, for example, a concave portion, a hole portion, or a convex portion having a small protruding height, the receiving surface may not necessarily be copied. This eliminates an unnecessary gap between the ceramic molded body and the bed, and in the degreasing process, the binder can be prevented from remaining near the surface of the ceramic molded body and the degreased body, and is easily deformed by the softening of the binder. In addition, the ceramic molded body can be more accurately supported, and harmful swelling, cracking or deformation of the degreased body can be suppressed. Further, since the degreased body can be accurately supported in the firing process, harmful deformation of the degreased body that shrinks due to the sintering of the ceramic powder can be suppressed. Therefore, it is possible to form a ceramic sintered body having a smaller dimensional variation with respect to a target outer dimension.
本発明に係る上述した寝床は、被測定箇所に対して垂直方向に測定した表面硬さが０．２〜４０ｋＰａの分布となる受け面を有するように形成することが好ましい。当該表面硬さの測定方法については実施例で詳述するが、セラミック成形体の被載置部が接触する寝床の受け面において数点を選び、その円錐圧子を被測定箇所に対して垂直方向に押し当てて所定の深さだけ埋め込んだときの荷重を測定し、各測定点について測定した荷重値を円錐圧子の接触面積（円錐圧子における底面を除く表面積）で除した値を表面硬さとして用いている。寝床の受け面の表面硬さが上記範囲であれば、粉末材料の相互の係合によって形成される空隙が好適な状態で形成される。このため、寝床は、セラミック成形体から溶融したバインダの浸透性と、セラミック成形体の重さを受けるための機械的強度の両方を、好適に備えることができる。また、寝床の受け面が変形する可能性は重力の作用方向や受け持つ負荷の程度にもよるが、受け面の表面硬さが０．２ｋＰａ未満であると、バインダの浸透性は高まるもののバインダの浸透による変形が大きくなりやすい。また、受け面の表面硬さが４０ｋＰａを超えると、受け面の機械的強度は高まるもののバインダの浸透性が低下しやすくなる。 The above-described bed according to the present invention is preferably formed so as to have a receiving surface having a surface hardness measured in a direction perpendicular to the measurement site of 0.2 to 40 kPa. The measuring method of the surface hardness will be described in detail in the examples, but several points are selected on the receiving surface of the bed where the mounting portion of the ceramic molded body comes into contact, and the conical indenter is perpendicular to the measurement location. Measure the load when it is pressed down to the specified depth and divide the load value measured at each measurement point by the contact area of the conical indenter (surface area excluding the bottom surface of the conical indenter) as the surface hardness. Used. If the surface hardness of the receiving surface of the bed is in the above range, the void formed by the mutual engagement of the powder material is formed in a suitable state. For this reason, the bed can suitably have both the permeability of the binder melted from the ceramic molded body and the mechanical strength for receiving the weight of the ceramic molded body. In addition, the possibility that the receiving surface of the bed is deformed depends on the direction of gravity and the degree of load, but if the surface hardness of the receiving surface is less than 0.2 kPa, the permeability of the binder increases, but the binder Deformation due to penetration tends to increase. On the other hand, if the surface hardness of the receiving surface exceeds 40 kPa, the mechanical strength of the receiving surface increases, but the permeability of the binder tends to decrease.
上述した寝床をなす粉末材料は、メジアン径ｄ５０が３〜４０μｍの粉末を用いることが好ましい。粉末のメジアン径ｄ５０が上記範囲内であれば、粉末の相互連結により形成される空隙の大きさ（細孔径）やその空隙の割合（空隙率）が好ましくなる。寝床が、適度に小さな細孔径と、適度に大きな空隙率とを有して形成されていると、毛細管現象の発現によりバインダが浸透しやすくなり、しかもバインダが浸透しても崩れて変形し難くなる。特に、受け面の表面近傍の内部形態の影響は大きい。その粉末のメジアン径ｄ５０が３μｍ未満になると空隙率が大きくなるため、バインダが浸透すると崩れやすくなる。また、その粉末のメジアン径ｄ５０が４０μｍを超えると細孔径が大きくなるため、毛細管現象によるバインダの浸透性が低下しやすくする。なお、粉末が３０μｍ以下のメジアン径ｄ５０であると、バインダの浸透性や耐変形性がより好ましくなる。なお、本発明でいうメジアン径ｄ５０は、体積粒度分布（横軸が粒径、縦軸が累積）における粒径の中央値である。 The powder material forming the bed described above is preferably a powder having a median diameter d 50 of 3 to 40 μm. When the median diameter d 50 of the powder is within the above range, the size of the voids (pore diameter) formed by the interconnection of the powders and the ratio of the voids (porosity) are preferable. When the bed is formed with a moderately small pore size and a moderately large porosity, the binder phenomenon is likely to penetrate due to the occurrence of capillary action, and even if the binder penetrates, it is difficult to collapse and deform. Become. In particular, the influence of the internal form near the surface of the receiving surface is great. When the median diameter d 50 of the powder is less than 3 μm, the porosity increases, and therefore, when the binder penetrates, the powder tends to collapse. Further, when the median diameter d 50 of the powder exceeds 40 μm, the pore diameter becomes large, so that the permeability of the binder due to the capillary phenomenon is easily lowered. When the powder has a median diameter d 50 of 30 μm or less, the permeability and deformation resistance of the binder are more preferable. The median diameter d 50 referred to in the present invention is the median value of the particle size in the volume particle size distribution (the horizontal axis is the particle size and the vertical axis is the accumulation).
また、上述した粉末材料としては、一般に入手性のよい結晶性シリカ粉末を用いることが好ましい。結晶性シリカ粉末は、セラミック成形体を構成する各種のバインダや、例えば、溶融シリカ、アルミナ、ジルコニアなどからなるセラミック粉末との反応性が低い。このため、脱脂工程の後の脱脂体や焼成工程の後のセラミック焼結体を、寝床から容易に分離することができる。また、セラミック焼結体の表面に結晶性シリカ粉末が異物となって固着することもない。 Moreover, as the powder material described above, it is preferable to use crystalline silica powder that is generally available. The crystalline silica powder has low reactivity with various binders constituting the ceramic molded body and ceramic powder made of, for example, fused silica, alumina, zirconia, or the like. For this reason, the degreased body after the degreasing step and the ceramic sintered body after the firing step can be easily separated from the bed. Further, the crystalline silica powder does not become a foreign substance and adhere to the surface of the ceramic sintered body.
また、上述した結晶性シリカとしては、脱脂や焼結における処理温度を考慮し、二酸化ケイ素の結晶多形のひとつで高温域でも安定なクリストバライト（クリストバル石、方珪石）の粉末が使用できる。この他にも、トリジマイトや石英などが使用できる。なお、結晶性シリカ粉末には、一般に、Ａｌ２Ｏ３やＦｅ２Ｏ３といった成分が含まれることがあり、これらは本発明においては添加を意図しない不可避的不純物として取り扱う。これらは、結晶性シリカ粉末および不可避的不純物の全体量あたり０．２質量％以下の含有量に抑えることが好ましい。 In addition, as the crystalline silica described above, a cristobalite (cristobalite, calcite) powder which is one of the crystalline polymorphs of silicon dioxide and is stable even at high temperatures can be used in consideration of the processing temperature in degreasing and sintering. In addition, tridymite or quartz can be used. The crystalline silica powder generally contains components such as Al 2 O 3 and Fe 2 O 3 , and these are treated as inevitable impurities not intended to be added in the present invention. These are preferably suppressed to a content of 0.2% by mass or less per the total amount of crystalline silica powder and inevitable impurities.
次に、本発明に係る上述した寝床の好ましい形成方法について説明する。
本発明に用いられる寝床の形成方法としては、例えば、サヤ内に充填した粉末材料の表面に、セラミック成形体を直接押し付けて形状を転写することで、受け面の形状を得る簡便な方法がある。
また、例えば、セラミック成形体の被載置部に対応する形状の転写部を有する模型を使用する方法がある。この場合、サヤ内に充填した粉末材料の表面に、その模型の転写部を直接押し付けて形状を転写することで、受け面の形状を得ることができる。この方法は、セラミック成形体の表面が損傷する可能性のある粉末材料への直接の押し付けを要さないため好ましい。
Next, a preferred method for forming the bed according to the present invention will be described.
As a method for forming the bed used in the present invention, for example, there is a simple method for obtaining the shape of the receiving surface by directly pressing the ceramic molded body onto the surface of the powder material filled in the sheath to transfer the shape. .
Further, for example, there is a method of using a model having a transfer portion having a shape corresponding to the placement portion of the ceramic molded body. In this case, the shape of the receiving surface can be obtained by transferring the shape by directly pressing the transfer portion of the model onto the surface of the powder material filled in the sheath. This method is preferable because it does not require direct pressing on the powder material that may damage the surface of the ceramic molded body.
また、上述した模型を容器内に設置し、その転写部を被覆するように粉末材料を充填し、その後に容器に振動を加えることにより、容器内の粉末材料を密な充填状態にする方法がある。加振を適用すれば、好適な充填状態の寝床を安定して作製できる。また、加振を制御することにより、被測定箇所に対して垂直方向に測定した受け面における表面硬さを制御することも可能である。 Also, there is a method in which the above-described model is placed in a container, filled with a powder material so as to cover the transfer portion, and then the container is vibrated to bring the powder material in the container into a densely filled state. is there. If excitation is applied, a bed in a suitable filling state can be stably produced. Further, by controlling the vibration, it is possible to control the surface hardness of the receiving surface measured in the direction perpendicular to the measurement site.
次に、本発明に係る上述した寝床の好ましい使用について説明する。
本発明に係る寝床を用い、セラミック粉末とバインダを含んで形成されているセラミック成形体を、脱脂工程および焼結工程において前記寝床に設けた受け面で支持し、セラミック焼結体を形成できる。その際に、前記脱脂工程は、バインダが分解し始めてから後述する目標温度に到達するまでの低温脱脂工程と、前記低温脱脂工程より高い温度による高温脱脂工程とを行う２段階の脱脂工程とすることが好ましい。
Next, the preferred use of the above-described bed according to the present invention will be described.
Using the bed according to the present invention, a ceramic molded body formed including ceramic powder and a binder can be supported by a receiving surface provided on the bed in the degreasing step and the sintering step, thereby forming a ceramic sintered body. At that time, the degreasing step is a two-step degreasing step in which a low-temperature degreasing step until the target temperature described below is reached after the binder starts to decompose and a high-temperature degreasing step at a higher temperature than the low-temperature degreasing step are performed. It is preferable.
本発明において、低温脱脂とは、雰囲気温度をバインダの分解開始温度を超えて目標温度まで昇温する過程において、あるいは昇温から目標温度到達後にその温度を保持する過程において、セラミック成形体に含まれるバインダを除去する処理（脱脂）をいう。その際の目標温度は、バインダの材質や昇温速度および目標温度到達後の保持時間など諸条件を考慮して調整できる。バインダの材質を考慮した場合の目標温度は２３０〜３５０℃が好ましく、例えば、パラフィンワックス系であれば２３０〜２７０℃、ＰＥＧ（ポリエチレングリコール）系であれば３００〜３５０℃が好ましい。また、上述した昇温速度、目標温度、保持時間などは、後述する低温脱脂後のセラミック成形体（半脱脂成形体）の残留バインダ量（低温脱脂前後のバインダ質量比）を考慮して決めることが好ましい。 In the present invention, low temperature degreasing is included in the ceramic molded body in the process of raising the ambient temperature to the target temperature exceeding the decomposition start temperature of the binder, or in the process of holding the temperature after reaching the target temperature from the temperature rise. This refers to the treatment (degreasing) for removing the binder. In this case, the target temperature can be adjusted in consideration of various conditions such as the binder material, the heating rate, and the holding time after reaching the target temperature. When considering the binder material, the target temperature is preferably 230 to 350 ° C., for example, 230 to 270 ° C. for a paraffin wax system and 300 to 350 ° C. for a PEG (polyethylene glycol) system. In addition, the above-described temperature increase rate, target temperature, holding time, etc. are determined in consideration of the residual binder amount (binder mass ratio before and after low temperature degreasing) of a ceramic molded body (semi-degreasing molded body) after low temperature degreasing described later. Is preferred.
また、高温脱脂とは、低温脱脂よりも雰囲気温度の目標を高く例えば６００℃に設定し、その目標温度に昇温する過程において、あるいは前記目標温度に到達後に適正な時間保持する過程において、半脱脂成形体に残存するバインダをさらに除去する処理（脱脂）をいう。例えば、低温脱脂を経た半脱脂成形体を焼結炉内に載置し、半脱脂成形体に含まれるセラミック粉末を焼結させる前段の昇温過程で脱脂（高温脱脂）し、引き続き焼結温度まで昇温してセラミック粉末の焼結を行う場合、高温脱脂工程から焼結工程までを一つの焼結炉で行う工程といえる。 In addition, high temperature degreasing is a process in which the target of the ambient temperature is set higher than that of low temperature degreasing, for example, 600 ° C., and the temperature is raised to the target temperature, or in the process of maintaining an appropriate time after reaching the target temperature. The treatment (degreasing) for further removing the binder remaining in the degreased molded body. For example, a semi-degreasing molded body that has undergone low-temperature degreasing is placed in a sintering furnace, degreased (high-temperature degreasing) in the temperature rising process before the ceramic powder contained in the semi-degreasing molded body is sintered, and then the sintering temperature When the ceramic powder is sintered at an elevated temperature, it can be said that the process from the high temperature degreasing process to the sintering process is performed in one sintering furnace.
低温脱脂を行う場合、寝床（低温脱脂用寝床）の受け面における表面硬さを０．２〜１０ｋＰａとすることが好ましい。当該表面硬さが０．２ｋＰａ未満である場合、セラミック成形体から溶融されたバインダを吸収する高い浸透性を有することができるものの、セラミック成形体の重さを受けるために必要な機械的強度が損なわれやすい。低温脱脂中に寝床が好ましくない変形を生じてしまうと、脱脂途中にあるセラミック成形体が寝床の変形形状に倣うように変形してしまうことがあるため好ましくない。また、当該表面硬さが１０ｋＰａを超える場合、寝床の受け面とセラミック成形体との接触による摩擦抵抗が小さくなるためセラミック成形体が寝床の受け面上を摺動しやすくなる。このため、寝床の受け面がセラミック成形体を拘束する作用が弱まり、セラミック成形体に含まれるバインダの溶融や膨張によってセラミック成形体が大きな変形を生じやすくなる。脱脂途中にあるセラミック成形体の大きな変形は、予測外の好ましくない形状に形成されることがあるため好ましくない。寝床の受け面の表面硬さの適正化は、セラミック成形体の予測外の好ましくない変形を抑制する効果があり、セラミック成形体が大型になるほど効果的である。 When performing low temperature degreasing, it is preferable that the surface hardness of the receiving surface of the bed (low temperature degreasing bed) is 0.2 to 10 kPa. When the surface hardness is less than 0.2 kPa, the mechanical strength necessary to receive the weight of the ceramic molded body can be obtained although it can have high permeability to absorb the binder melted from the ceramic molded body. It is easily damaged. If the bed is undesirably deformed during the low temperature degreasing, the ceramic molded body in the middle of the degreasing may be deformed to follow the deformed shape of the bed, which is not preferable. Further, when the surface hardness exceeds 10 kPa, the frictional resistance due to the contact between the receiving surface of the bed and the ceramic molded body is reduced, so that the ceramic molded body can easily slide on the receiving surface of the bed. For this reason, the effect | action which the receiving surface of a bed restrains a ceramic molded object becomes weak, and a ceramic molded object becomes easy to produce a big deformation | transformation by melting and expansion | swelling of the binder contained in a ceramic molded object. A large deformation of the ceramic molded body in the middle of degreasing is not preferable because it may be formed in an unexpected and undesirable shape. The optimization of the surface hardness of the receiving surface of the bed has an effect of suppressing unexpected and undesirable deformation of the ceramic molded body, and is more effective as the ceramic molded body becomes larger.
低温脱脂を経て、バインダの量が低減して半脱脂の状態になったセラミック成形体（半脱脂成形体）は、次いで高温脱脂を行う際に損傷、崩壊、変形といった不具合を生じやすくなる。そこで、高温脱脂を行う場合、あるいは高温脱脂からそのまま焼結を行う場合、表面硬さよりも表面の滑りやすさを重視した受け面を有する寝床が好ましい。この場合、寝床（高温脱脂用寝床）の受け面における表面硬さを２〜４０ｋＰａであると、寝床の受け面が滑りやすい傾向を示すようになる。なお、当該表面硬さが２ｋＰａ未満であると、低温脱脂後の半脱脂成形体の保形が容易でなくり、当該表面硬さが４０ｋＰａを超えると、高温脱脂から焼結する工程において割れが生じることがある。上述した表面の滑りやすさの観点から言えば、半脱脂成形体の自重が大きく作用する寝床の受け面の底部などでは、当該表面硬さを１０〜４０ｋＰａと高目に設定し、当該底部と半脱脂成形体の間の摩擦抵抗を下げておくことが好ましい。これにより、半脱脂成形体が高温脱脂から焼結を経て大きな収縮をしながら緻密化されていく間に、予測外の好ましくない変形の発生を低減することができる。 A ceramic molded body (semi-degreasing molded body) that has been subjected to low-temperature degreasing to be in a semi-degreasing state with a reduced amount of binder is liable to cause problems such as damage, collapse, and deformation when performing high-temperature degreasing. Therefore, when high temperature degreasing is performed or when sintering is performed as it is from high temperature degreasing, a bed having a receiving surface in which the surface slipperiness is more important than the surface hardness is preferable. In this case, when the surface hardness of the receiving surface of the bed (the bed for high temperature degreasing) is 2 to 40 kPa, the receiving surface of the bed tends to be slippery. In addition, if the surface hardness is less than 2 kPa, it is not easy to retain the shape of the semi-degreasing molded body after low-temperature degreasing, and if the surface hardness exceeds 40 kPa, cracking occurs in the process of sintering from high-temperature degreasing. May occur. Speaking from the viewpoint of the slipperiness of the surface described above, at the bottom of the receiving surface of the bed where the weight of the semi-degreasing molded body acts greatly, the surface hardness is set to 10 to 40 kPa, and the bottom and It is preferable to reduce the frictional resistance between the semi-degreasing molded bodies. Thereby, generation | occurrence | production of an unexpected undesirable deformation | transformation can be reduced, while a semi-degreasing molded object is densified through large shrinkage | contraction through sintering from high temperature degreasing | defatting.
上述した低温脱脂においては、セラミック成形体に含まれるバインダの残量が、低温脱脂前後のバインダ質量比で１０〜２０％になるように行うことが好ましい。これにより、ハンドリングのために少なくとも必要な機械的強度を有する半脱脂成形体に形成できるため、その後の例えば高温脱脂前に寝床の交換などを行う場合など、半脱脂成形体のハンドリングなどの取り扱いが容易になる。 The low-temperature degreasing described above is preferably performed so that the remaining amount of the binder contained in the ceramic molded body is 10 to 20% in terms of the binder mass ratio before and after the low-temperature degreasing. As a result, it can be formed into a semi-degreasing molded body having at least the necessary mechanical strength for handling, and therefore handling such as handling of the semi-degreasing molded body such as when replacing a bed before high temperature degreasing, etc. It becomes easy.
また、上述した低温脱脂において、バインダが分解し始めた後は、昇温速度を５℃／ｈ以下に設定することが好ましい。より好ましくは３℃／ｈ以下である。セラミック成形体に含まれるバインダは、昇温に伴って膨張し、分解温度を超えると急激に膨張しつつ気化し始めると考えられる。よって、低温域であっても速すぎる昇温は、セラミック成形体に膨れ、割れ、変形といった不具合を生じやすくなり、その後の高温脱脂や焼結において前記不具合を引き起こす微細な起点が形成されやすくなる。一方、バインダが分解し始める以前は、あまりにも急激な昇温はセラミック成形体の変形を誘発する可能性があることや、量産として常識的な処理時間（タクトタイム）になることなどを考慮し、昇温速度を５℃／ｈ〜１０℃／ｈに設定することが好ましい。より好ましくは７℃／ｈ以下である。 In the above-described low temperature degreasing, it is preferable to set the rate of temperature rise to 5 ° C./h or less after the binder starts to decompose. More preferably, it is 3 ° C./h or less. It is considered that the binder contained in the ceramic molded body expands as the temperature rises and starts to vaporize while rapidly expanding when the decomposition temperature is exceeded. Therefore, too high a temperature rise even in a low temperature range tends to cause defects such as swelling, cracking and deformation of the ceramic molded body, and a fine starting point that causes the defects in subsequent high-temperature degreasing and sintering is likely to be formed. . On the other hand, before the binder starts to decompose, taking into account the fact that an excessively high temperature can induce deformation of the ceramic molded body and that it becomes a common-sense processing time (tact time) for mass production. It is preferable to set the rate of temperature rise to 5 ° C./h to 10 ° C./h. More preferably, it is 7 ° C./h or less.
また、前記低温脱脂工程と前記高温脱脂工程の間で前記寝床を交換し、前記高温脱脂工程に続いて前記焼結工程を行うことが好ましい。低温脱脂工程と高温脱脂工程の間で寝床を交換する場合、低温脱脂を行う場合に用いる寝床の受け面における表面硬さよりも、高温脱脂を行う場合に用いる寝床の受け面における表面硬さを高くすることが好ましい。このように低温脱脂工程後に寝床を交換することで、高温脱脂工程においても本発明に係る寝床による上述した作用効果を改めて得ることができる。 Moreover, it is preferable to replace the bed between the low temperature degreasing step and the high temperature degreasing step, and to perform the sintering step subsequent to the high temperature degreasing step. When replacing a bed between a low temperature degreasing process and a high temperature degreasing process, the surface hardness of the bed receiving surface used for high temperature degreasing is higher than the surface hardness of the bed receiving surface used for low temperature degreasing. It is preferable to do. Thus, by exchanging the bed after the low-temperature degreasing step, the above-described effects of the bed according to the present invention can be obtained again even in the high-temperature degreasing step.
次に、本発明に係るセラミック焼結体の製造方法について、図１〜図３を用いて説明する。また、本発明に係る製造方法を適用した実施例１、２、４、６を表１に示す。なお、表１に実施例１、２、４、６として示す脱脂体、並びにセラミック焼結体には、以下の手順で同様に作製したセラミック成形体を用いた。 Next, the manufacturing method of the ceramic sintered compact concerning this invention is demonstrated using FIGS. 1-3. In addition, Table 1 shows Examples 1 , 2, 4 , and 6 to which the manufacturing method according to the present invention is applied. In addition, the ceramic molded body produced similarly in the following procedures was used for the degreased body shown in Table 1 as Examples 1 , 2, 4, and 6 and the ceramic sintered body.
まず、図３に断面で示すセラミック成形体１を、セラミック成形体の主成分である溶融シリカ粉末にアルミナ粉末やジルコン粉末などを添加した混合粉（セラミック粉末）とパラフィンワックス系バインダを含む射出成形用組成物を用い、射出成形法によって作製した。なお、射出成形用組成物について、実施例１と、実施例２と、実施例４と、実施例６とでは溶融シリカ（結晶性シリカ）粉末のメジアン径ｄ５０を違え、その他の粉末やバインダは一定とした。得られたセラミック成形体１の寸法は、概ね、長さ３００ｍｍ、幅１００ｍｍ、厚肉部の厚さ１５ｍｍである。 First, the ceramic molded body 1 shown in cross section in FIG. 3 is injection molded including a mixed powder (ceramic powder) obtained by adding alumina powder, zircon powder or the like to fused silica powder, which is the main component of the ceramic molded body, and a paraffin wax binder. It was produced by an injection molding method using the composition for use. Note that the injection molding composition, as in Example 1, Example 2, Example 4, in Example 6 Chigae a median size d 50 of fused silica (crystalline silica) powder, other powders and the binder Was constant. The dimensions of the obtained ceramic molded body 1 are approximately 300 mm in length, 100 mm in width, and 15 mm in thickness of the thick part.
次に、セラミック成形体１を脱脂工程および焼成工程において載置する図３に断面で示す受け面２ａを有する寝床２を、以下の手順で作製した。
まず、図１に示すように、板４上に環状の枠５を配置し、その枠５の中にセラミック成形体１の被載置部に対応する形状の転写部７ａを有する押し型７を設置する。さらに、その枠５の中に、結晶性シリカ粉末２’（粉末材料）を押し型７との間に隙間ができないように充填し、サヤ３の底板６を用いて蓋をした。そして、図２に示すように押し型７が上側で底板６が下側になるように反転し、サヤ３内の結晶性シリカ粉末２’ができるだけ均一な充填状態になるように、その状態で振動を加えた。その後、押し型７を取り外すことで、セラミック成形体１の被載置部に対応する形状の受け面２ａを有する図３に示す寝床２を得た。このような手段によれば、寝床２の受け面２ａにセラミック成形体１を載置したとき、セラミック成形体１の自重が大きく作用する受け面２ａの底部やその近傍では表面硬さが高くなり、表１で示す範囲（最小〜最大）の表面硬さの範囲を有する寝床２の受け面２ａを得ることができる。また、加える振動の大きさや周波数を変えることで、寝床の受け面を表１で示す表面硬さに形成した。
Next, a bed 2 having a receiving surface 2a shown in cross section in FIG. 3 on which the ceramic molded body 1 is placed in the degreasing step and the firing step was produced by the following procedure.
First, as shown in FIG. 1, an annular frame 5 is arranged on a plate 4, and a pressing die 7 having a transfer portion 7 a having a shape corresponding to the placement portion of the ceramic molded body 1 is placed in the frame 5. Install. Further, in the frame 5, the crystalline silica powder 2 ′ (powder material) was filled so that there was no gap between the mold 7 and the bottom plate 6 of the sheath 3 was covered. Then, as shown in FIG. 2, the pressing die 7 is inverted so that the bottom plate 6 is on the lower side, and the crystalline silica powder 2 'in the sheath 3 is filled in as uniform a state as possible. Vibration was applied. Then, the bed 2 shown in FIG. 3 which has the receiving surface 2a of the shape corresponding to the mounting part of the ceramic molded body 1 was obtained by removing the press die 7. Then, as shown in FIG. According to such a means, when the ceramic molded body 1 is placed on the receiving surface 2a of the bed 2, the surface hardness increases at the bottom of the receiving surface 2a where the weight of the ceramic molded body 1 acts greatly and in the vicinity thereof. The receiving surface 2a of the bed 2 having a surface hardness range in the range shown in Table 1 (minimum to maximum) can be obtained. Moreover, the receiving surface of the bed was formed to the surface hardness shown in Table 1 by changing the magnitude and frequency of the applied vibration.
なお、寝床を形成する結晶性シリカ粉末の粒度は、レーザー回折・散乱式粒度分布測定装置を用いて測定した。また、寝床２の受け面２ａの表面硬さは、先端に円錐圧子（底面直径４．５ｍｍ、高さ６ｍｍ）を取り付けたデジタルフォースゲージにより測定した荷重値を用いて算出した。具体的には、セラミック成形体の被載置部が接触する寝床の受け面において１５点を選び、その円錐圧子を被測定箇所に対して垂直方向に押し当てて６ｍｍだけ埋め込んだときの荷重を測定した。そして、各測定点について、測定した荷重値を円錐圧子の接触面積（円錐圧子における底面を除く表面積）で除し、その値を表面硬さとした。 The particle size of the crystalline silica powder forming the bed was measured using a laser diffraction / scattering particle size distribution analyzer. The surface hardness of the receiving surface 2a of the bed 2 was calculated using a load value measured by a digital force gauge having a conical indenter (bottom diameter 4.5 mm, height 6 mm) attached to the tip. Specifically, 15 points are selected on the receiving surface of the bed on which the placing portion of the ceramic molded body comes into contact, and the load when the cone indenter is pressed in the vertical direction with respect to the measurement location and embedded by 6 mm is applied. It was measured. And about each measuring point, the measured load value was remove | divided by the contact area (surface area except the bottom face in a conical indenter) of the conical indenter, and the value was made into surface hardness.
次に、脱脂工程および焼成工程を経て、セラミック成形体１を用いてセラミック焼結体を作製した。具体的には、以下の手順で行った。
（第１の実施形態）
まず、図３に示すように、セラミック成形体１をその被載置部が寝床２の受け面２ａに対応するように載置した。そして、セラミック成形体１と寝床２およびサヤ３を図３に示す状態で脱脂炉に入れ、所定の脱脂条件（温度５８０℃で保持６ｈ）で処理して僅かなバインダが残存して保形するセラミック脱脂体に形成し、そのまま炉冷した。その後、そのセラミック脱脂体を焼成炉に移し替え、所定の焼成条件（温度１３００℃で保持２ｈ）で処理してセラミック粉末を焼結し、そのまま炉冷してセラミック焼結体を得た。なお、セラミック焼結体は寝床から容易に分離できた。作製したセラミック焼結体の寸法は、三次元デジタイザ（ＧＯＭ社製ＡＴＯＳ）を用いて測定した。
Next, a ceramic sintered body was produced using the ceramic molded body 1 through a degreasing step and a firing step. Specifically, the following procedure was used.
(First embodiment)
First, as shown in FIG. 3, the ceramic molded body 1 was placed such that the placement portion thereof corresponds to the receiving surface 2 a of the bed 2. Then, the ceramic molded body 1, the bed 2 and the sheath 3 are put in a degreasing furnace in the state shown in FIG. 3, and are processed under predetermined degreasing conditions (temperature is maintained at 580 ° C. for 6 hours) to retain a slight amount of binder. It formed in the ceramic degreased body and cooled as it was . Thereafter, the ceramic degreased body was transferred to a firing furnace, treated under predetermined firing conditions (temperature maintained at 1300 ° C. for 2 hours) to sinter the ceramic powder, and cooled as it was to obtain a ceramic sintered body. The ceramic sintered body was easily separated from the bed. The dimension of the produced ceramic sintered compact was measured using the three-dimensional digitizer (ATOS by GOM).
以上の結果、表１中「脱脂体」で示すセラミック脱脂体について、実施例１、２、４では、明確かつ有害な膨れや割れが認められなかった（表１中「○」で示す）。また、実施例６では、割れが認められた（表１中「△」で示す）ものの軽微で有害という程ではなく、補修により使用できた。また、表１で示す実施例２で用いたセラミック成形体と同等のセラミック成形体を、寝床２と同等の溶融シリカ粉末を平坦に敷き詰めて表面硬さを１５〜２０ｋＰａの範囲内に形成したサヤの上に静置し、実施例２と同等の脱脂工程で処理したところ、得られたセラミック脱脂体は割れが原因と推測できる損壊が発生した。 As a result, clear and harmful blisters and cracks were not observed in Examples 1 , 2, and 4 with respect to the ceramic degreased body indicated by “Degreased body” in Table 1 (indicated by “◯” in Table 1). Moreover, in Example 6 , although cracking was recognized (indicated by “Δ” in Table 1), it was not so slight and harmful, and could be used by repair. In addition, a ceramic molded body equivalent to the ceramic molded body used in Example 2 shown in Table 1 was flattened with a fused silica powder equivalent to the bed 2 and the surface hardness was formed within a range of 15 to 20 kPa. When this was left to stand and treated in a degreasing step equivalent to that in Example 2, the obtained ceramic degreased body was damaged which could be assumed to be caused by cracking.
セラミック焼結体においては、実施例１、２、４では、有害な膨れや割れが認められず（表１中「○」で示す）、外形寸法バラツキ（変形）も小さかった（±２．２ｍｍ）。実施例６では、膨れや割れが認められた（表１中「△」で示す）ものの軽微で有害という程ではなく、補修により使用できた。また、実施例６では、外形寸法バラツキ（変形）は小さかった（±１．９ｍｍ）。外形寸法バラツキについて、実施例２、４、６はそれぞれ±０．９、±１．４、±１．４と小さくなった。これは、寝床の受け面における表面硬さが０．２〜４０ｋＰａの範囲であること、並びに、寝床を形成する粉末材料の体積粒度分布におけるメジアン径ｄ５０が３〜４０μｍであることによると推測できる。
また、いずれのセラミック焼結体に対しても、寝床を形成している結晶性シリカ粉末が固着するようなことがなかった。
In the ceramic sintered bodies, no harmful blisters or cracks were observed in Examples 1 , 2, and 4 (indicated by “◯” in Table 1), and the external dimension variation (deformation) was small (± 2.2 mm). ). In Example 6 , blistering and cracking were observed (indicated by “Δ” in Table 1), but they were not slight and harmful, and could be used by repair. Moreover , in Example 6 , the external dimension variation (deformation) was small (± 1.9 mm). Regarding the variation in outer dimensions, Examples 2, 4, and 6 were as small as ± 0.9, ± 1.4, and ± 1.4, respectively. This is presumably due to the fact that the surface hardness at the receiving surface of the bed is in the range of 0.2 to 40 kPa, and that the median diameter d 50 in the volume particle size distribution of the powder material forming the bed is 3 to 40 μm. it can.
In addition, the crystalline silica powder forming the bed did not stick to any ceramic sintered body.
（第２の実施形態）
上述した第１の実施形態で用いたセラミック成形体よりも大きい、長さ４００ｍｍ、幅１１０ｍｍ、厚肉部の厚さ１５ｍｍのセラミック成形体を用い、第１の実施形態とは別の手順により、脱脂工程および焼成工程を経て、セラミック焼結体を作製した。以下、第２の実施形態に係る説明においては、便宜上、上述した第１の実施形態で用いた各図および各部品の名称や番号をそのまま引用する。
(Second Embodiment)
Using a ceramic molded body having a length of 400 mm, a width of 110 mm, and a thickness of 15 mm, which is larger than the ceramic molded body used in the first embodiment described above, according to a procedure different from that of the first embodiment, A ceramic sintered body was produced through a degreasing step and a firing step. Hereinafter, in the description according to the second embodiment, for the sake of convenience, the drawings and the names and numbers of the components used in the first embodiment described above are cited as they are.
まず、第２の実施形態においても同様に、図３に示すように、セラミック成形体１をその被載置部が寝床２の受け面２ａに対応するように載置した。寝床２には、受け面２ａにおける表面硬さを１．８〜４．４ｋＰａに形成したもの（後述する表２中「実施例９」で示す）と、３．５〜１３．９ｋＰａに形成したもの（後述する表２中「実施例１０」で示す）を用いた。そして、セラミック成形体１と寝床２およびサヤ３を図３に示す状態で脱脂炉に入れて、低温脱脂を行った。まず、脱脂炉の昇温速度を６℃／ｈに設定し、セラミック成形体１に含まれるパラフィンワックス系バインダを含む射出成形用組成物（以下、「バインダ」という。）が分解し始める雰囲気温度に至るまで昇温した。次いで、脱脂炉の昇温速度を３℃／ｈに変更し、雰囲気温度が２４０℃に至るまでさらに昇温し、２４０℃到達後は特段の温度保持をしないで降温した。この低温脱脂により、セラミック成形体１に含まれるバインダを除去し、セラミック脱脂体（半脱脂成形体）を形成した。セラミック脱脂体（半脱脂成形体）におけるバインダの残量は、［バインダの残量］（％）＝（［脱脂前のセラミック成形体に含まれるバインダの質量］−［脱脂後のセラミック成形体（半脱脂成形体）に含まれるバインダの質量］）／［脱脂前のセラミック成形体に含まれるバインダの質量］×１００、として算定した。 First, similarly in the second embodiment, as shown in FIG. 3, the ceramic molded body 1 was placed so that the placement portion thereof corresponds to the receiving surface 2 a of the bed 2. The bed 2 has a surface hardness of 1.8 to 4.4 kPa (shown in “Example 9” in Table 2 to be described later) and 3.5 to 13.9 kPa. (Shown as “Example 10” in Table 2 below) was used. And the ceramic molded object 1, the bed 2, and the sheath 3 were put into the degreasing furnace in the state shown in FIG. 3, and low temperature degreasing was performed. First, the temperature rise rate of the degreasing furnace is set to 6 ° C./h, and the ambient temperature at which the composition for injection molding (hereinafter referred to as “binder”) containing the paraffin wax binder contained in the ceramic molded body 1 begins to decompose. The temperature was raised to Next, the temperature raising rate of the degreasing furnace was changed to 3 ° C./h, and the temperature was further raised until the atmospheric temperature reached 240 ° C. After reaching 240 ° C., the temperature was lowered without particularly maintaining the temperature. By this low temperature degreasing, the binder contained in the ceramic molded body 1 was removed to form a ceramic degreased body (semi-degreasing molded body). The remaining amount of binder in the ceramic degreased body (semi-degreasing molded body) is [residual amount of binder] (%) = ([mass of binder contained in ceramic molded body before degreasing] − [ceramic molded body after degreasing ( The mass of the binder contained in the semi-degreasing molded body))) / [the mass of the binder contained in the ceramic molded body before degreasing] × 100.
上述した低温脱脂の後、寝床２を別の寝床に交換した。交換後の寝床には、受け面における表面硬さを実施例９、１０ともに３．５〜１３．９ｋＰａに形成したものを用いた。なお、実施例１０は交換前後で同じ表面硬さであるが、交換後の寝床には低温脱脂によるバインダの付着や浸透がないため、高温脱脂においても本発明に係る寝床による作用効果を改めて得ることができるはずである。そして、セラミック脱脂体（半脱脂成形体）と新たな寝床およびサヤ３を焼結炉に入れ、所定の条件で昇温（途中、設定温度４００℃で２ｈ保持）しつつセラミック脱脂体（半脱脂成形体）からバインダを除去（高温脱脂）し、そのままさらに昇温（設定温度１３００℃で２ｈ保持）してセラミック粉末を焼結した。炉冷後、セラミック焼結体は寝床から容易に分離でき、本発明の実施例となるセラミック中子を得ることができた。なお、上述した焼結炉において、常温から４００℃までは１００℃／ｈで昇温し、その後は焼結保持温度１３００℃に至るまで２５℃／ｈで昇温した。 After the low-temperature degreasing described above, the bed 2 was replaced with another bed. For the bed after the replacement, the surface hardness on the receiving surface was set to 3.5 to 13.9 kPa in both Examples 9 and 10. In addition, Example 10 has the same surface hardness before and after the replacement, but since the bed after the replacement has no adhesion or penetration of the binder due to the low temperature degreasing, the effect of the bed according to the present invention can be obtained again even in the high temperature degreasing. Should be able to. Then, the ceramic degreased body (semi-degreasing molded body), a new bed and the sheath 3 are placed in a sintering furnace, and the temperature is raised under predetermined conditions (maintained at a set temperature of 400 ° C. for 2 hours). The binder was removed from the molded body (high temperature degreasing), and the temperature was further increased (held at a set temperature of 1300 ° C. for 2 hours) to sinter the ceramic powder. After the furnace cooling, the ceramic sintered body could be easily separated from the bed, and a ceramic core serving as an example of the present invention could be obtained. In the sintering furnace described above, the temperature was raised from room temperature to 400 ° C. at 100 ° C./h, and thereafter, the temperature was raised at 25 ° C./h until the sintering holding temperature reached 1300 ° C.
上述のようにして作製したセラミック焼結体の寸法は、三次元形状測定機（ミツトヨ製ＣＲＹＳＴＡ―ＡＰＥＸ）を用いて測定した。第２の実施形態を適用した実施例９、１０を表２に示す。 The dimensions of the ceramic sintered body produced as described above were measured using a three-dimensional shape measuring machine (CRYSTA-APEX manufactured by Mitutoyo). Examples 9 and 10 to which the second embodiment is applied are shown in Table 2.
以上の結果、表２中「脱脂体」で示すセラミック脱脂体について、実施例９では、明確かつ有害な膨れや割れが認められなかった（表２中「○」で示す）。実施例１０では、割れが認められた（表２中「△」で示す）ものの軽微で有害という程ではなく、補修により使用できた。また、実施例９、１０で示すセラミック脱脂体のハンドリング等の取扱いは容易であったが、それぞれのバインダの残量が１２．０％、１３．５％であったためと推測される。 As a result, clear and harmful blisters and cracks were not observed in Example 9 for the ceramic degreased body shown in Table 2 as “Degreased body” (indicated by “◯” in Table 2). In Example 10, although cracking was observed (indicated by “Δ” in Table 2), it was not so slight and harmful, and could be used by repair. Moreover, although handling of the ceramic degreased body shown in Examples 9 and 10 was easy, it is estimated that the remaining amount of each binder was 12.0% and 13.5%.
セラミック焼結体においては、実施例９では、有害な膨れや割れが認められず（表２中「○」で示す）、外形寸法バラツキ（変形）も小さかった（±１．２ｍｍ）。実施例１０では、割れが認められた（表２中「△」で示す）ものの軽微で有害という程ではなく、補修により使用でき、外形寸法バラツキ（変形）は小さかった（±１．３ｍｍ）。
また、いずれのセラミック焼結体（実施例９、１０）に対しても、寝床を形成している結晶性シリカ粉末が固着するようなことがなかった。
In the ceramic sintered body, no harmful blisters and cracks were observed in Example 9 (indicated by “◯” in Table 2), and the external dimension variation (deformation) was small (± 1.2 mm). In Example 10, although cracking was observed (indicated by “Δ” in Table 2), it was not so slight and harmful, it could be used by repair, and the external dimension variation (deformation) was small (± 1.3 mm).
In addition, the crystalline silica powder forming the bed was not fixed to any ceramic sintered body (Examples 9 and 10).
（第３の実施形態）
上述した第２の実施形態で用いたセラミック成形体と同様に、長さ４００ｍｍ、幅１１０ｍｍ、厚肉部の厚さ１５ｍｍのセラミック成形体を用い、第１および第２の実施形態とは別の手順により、脱脂工程を経て、セラミック脱脂体（半脱脂成形体）を作製した。以下、第３の実施形態に係る説明においても同様に、便宜上、上述した第１の実施形態で用いた各図および各部品の名称や番号をそのまま引用する。
(Third embodiment)
Similar to the ceramic molded body used in the second embodiment described above, a ceramic molded body having a length of 400 mm, a width of 110 mm, and a thickness of 15 mm is used, which is different from the first and second embodiments. A ceramic degreased body (semi-degreasing molded body) was produced through a degreasing process according to the procedure. Hereinafter, in the description according to the third embodiment as well, for convenience, the drawings and the names and numbers of the components used in the first embodiment described above are cited as they are.
まず、第３の実施形態においても同様に、図３に示すように、セラミック成形体１をその被載置部が寝床２の受け面２ａに対応するように載置した。寝床２には、受け面２ａにおける表面硬さを３．５〜１３．９ｋＰａに形成したもの（後述する表３中「実施例１１〜１３」で示す）を用いた。そして、セラミック成形体１と寝床２およびサヤ３を図３に示す状態で脱脂炉に入れて、低温脱脂を行った。この際に、脱脂炉の昇温速度を６℃／ｈに設定し、セラミック成形体１に含まれるパラフィンワックス系バインダを含む射出成形用組成物（以下、「バインダ」という。）が分解し始める雰囲気温度に至るまで昇温した。次いで、脱脂炉の昇温速度を後述する表３中の実施例１１〜１３それぞれで３℃／ｈ、１０℃／ｈ、３０℃／ｈに設定を変更し、それぞれの雰囲気温度が２４０℃に至るまでさらに昇温し、２４０℃到達後は特段の温度保持をしないで降温した。この低温脱脂により、セラミック成形体１に含まれるバインダを除去し、セラミック脱脂体（半脱脂成形体）を形成した。セラミック脱脂体（半脱脂成形体）におけるバインダの残量は、［バインダの残量］（％）＝（［脱脂前のセラミック成形体に含まれるバインダの質量］−［脱脂後のセラミック成形体（半脱脂成形体）に含まれるバインダの質量］）／［脱脂前のセラミック成形体に含まれるバインダの質量］×１００、として算定した。 First, similarly in the third embodiment, as shown in FIG. 3, the ceramic molded body 1 was placed such that the placement portion thereof corresponds to the receiving surface 2 a of the bed 2. As the bed 2, one having a surface hardness on the receiving surface 2 a of 3.5 to 13.9 kPa (shown as “Examples 11 to 13” in Table 3 described later) was used. And the ceramic molded object 1, the bed 2, and the sheath 3 were put into the degreasing furnace in the state shown in FIG. 3, and low temperature degreasing was performed. At this time, the temperature rising rate of the degreasing furnace is set to 6 ° C./h, and the composition for injection molding (hereinafter referred to as “binder”) including the paraffin wax binder contained in the ceramic molded body 1 starts to decompose. The temperature was raised to ambient temperature. Next, the temperature raising rate of the degreasing furnace was changed to 3 ° C./h, 10 ° C./h, and 30 ° C./h in each of Examples 11 to 13 in Table 3 to be described later, and the ambient temperature was 240 ° C. The temperature was further increased until reaching 240 ° C., and the temperature was decreased without particularly maintaining the temperature. By this low temperature degreasing, the binder contained in the ceramic molded body 1 was removed to form a ceramic degreased body (semi-degreasing molded body). The remaining amount of binder in the ceramic degreased body (semi-degreasing molded body) is [residual amount of binder] (%) = ([mass of binder contained in ceramic molded body before degreasing] − [ceramic molded body after degreasing ( The mass of the binder contained in the semi-degreasing molded body))) / [the mass of the binder contained in the ceramic molded body before degreasing] × 100.
上述のようにして作製したセラミック脱脂体の寸法を、三次元形状測定機（ミツトヨ製ＣＲＹＳＴＡ―ＡＰＥＸ）を用いて測定し、もとのセラミック成形体からの寸法変化を求めた。実施例１１〜１３を表３に示す。 The dimensions of the ceramic degreased body produced as described above were measured using a three-dimensional shape measuring machine (CRYSTA-APEX manufactured by Mitutoyo Corporation) to determine the dimensional change from the original ceramic molded body. Examples 3 to 13 are shown in Table 3.
以上の結果、表３中「脱脂体」で示すセラミック脱脂体について、実施例１１〜１３すべてに割れが認められた（表３中「△」で示す）ものの軽微で有害という程ではなく、補修により使用できた。また、実施例１１、１２で示すセラミック脱脂体のハンドリング等の取扱いは容易であったが、それぞれのバインダの残量が１２．８％、１４．２％であったためと推測される。また、実施例１３のバインダの残量は２４．５％であったが、実施例１１、１２と同様に、寝床から取り外すといった取扱いをすることができた。 As a result of the above, the ceramic degreased body indicated by “Degreased body” in Table 3 was repaired, not only to a slight and harmful degree, although cracks were observed in all of Examples 11 to 13 (indicated by “△” in Table 3). Could be used. Moreover, although handling of the ceramic degreased body shown in Examples 11 and 12 was easy, it is estimated that the remaining amount of each binder was 12.8% and 14.2%. Moreover, although the residual amount of the binder of Example 13 was 24.5%, it was able to be handled by removing from the bed as in Examples 11 and 12.
また、セラミック脱脂体の形状バラツキは、脱脂炉の昇温速度が遅いほど小さく、その後の焼成において、最終的に得られるセラミック焼成体の形状バラツキを制御しやすくなることが確認できた。 Moreover, the shape variation of the ceramic degreased body was smaller as the temperature increase rate of the degreasing furnace was slower, and it was confirmed that the shape variation of the finally obtained ceramic fired body can be easily controlled in the subsequent firing.
１ セラミック成形体
２ 寝床
２ａ 受け面
２’ 結晶性シリカ粉末
３ サヤ
４ 板
５ 枠
６ 底板
７ 押し型
７ａ 転写部
８ 翼形部
９ ダブテール
DESCRIPTION OF SYMBOLS 1 Ceramic molded body 2 Bedding bed 2a Receiving surface 2 'Crystalline silica powder 3 Saya 4 Board 5 Frame 6 Bottom board 7 Stamping die 7a Transfer part 8 Airfoil part 9 Dovetail
Claims (9)
前記セラミック成形体の被載置部に対応する形状の転写部を有する模型を容器内に設置し、前記セラミック成形体の焼結処理条件において焼結されない粉末材料を前記転写部を被覆するように前記容器内に充填して振動を加えることにより、前記寝床の前記受け面を、前記セラミック成形体の前記被載置部に対応する形状であって、被測定箇所に対して垂直方向に測定した表面硬さが０．２〜４０ｋＰａの範囲内であるように形成する、ことを特徴とするセラミック焼結体の製造方法。 A ceramic having an airfoil portion and a dovetail used for casting a gas turbine blade, wherein a ceramic formed body including ceramic powder and a binder is supported by a receiving surface provided on a bed in a degreasing process and / or a sintering process. A method of manufacturing a ceramic sintered body for forming a core ,
A model having a transfer portion having a shape corresponding to the placement portion of the ceramic molded body is placed in a container, and a powder material that is not sintered under the sintering process conditions of the ceramic molded body is covered with the transfer portion. by applying vibration to fill in the container, the receiving surface of the bed, said a said shape corresponding to the mounting portion of the ceramic molded bodies were measured in a direction perpendicular to the measured point It forms so that surface hardness may be in the range of 0.2-40 kPa, The manufacturing method of the ceramic sintered compact characterized by the above-mentioned .
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| JP2021165216A (en) * | 2020-04-08 | 2021-10-14 | 株式会社ミマキエンジニアリング | Method for manufacturing sintered product from three-dimensional molded article |
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